New drugs are urgently needed for cryptosporidiosis and toxoplasmosis for human and domestic livestock use. Cryptosporidiosis causes wasting diarrhea in humans and calves. Toxoplasmosis is an important cause of fetal malformations and abortions in humans and domestic livestock. In addition, an effective drug is also needed for veterinary use for neosporosis, the cause of epidemic abortions in livestock. This project follows on our successful hit-to-lead drug development project, targeting protozoan Calcium Dependent Protein Kinases (CDPKs). We now have two promising pre-clinical drug candidates that show activity in mouse models of cryptosporidiosis, toxoplasmosis and neosporosis, and thus are of great potential value for both veterinary and human health. The goal of this project will be to conduct efficacy, pharmacokinetic (PK), and toxicity testing of our novel therapeutics in agriculturally-important domestic animals (cattle and sheep) to show efficacy for animal diseases and to also gather information for the preclinical drug package for human use. We will scale-up the compounds to the near kilogram quantity, test their efficacy in sheep models of toxoplasmosis and neosporosis, and in a calf model of cryptosporidiosis. In the end of this project, the goal is to have a preclinical drug candidate and one or two backups to advance to final preclinical testing and IND/NADA registration for veterinary and human use.